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A refined full-order method is presented for estimating the extreme wind load effects of rigid structures with given mean recurrence intervals (MRIs) by combining the distributions of annual maximum wind speed and extreme load coefficients. This refined method is capable of dealing with any type of asymptotic extreme value distribution. With this full-order method, the predictions of wind load effects by using distributions of annual maximum wind velocity pressure and wind speed are compared that provide information on the sensitivity of predictions to the upper tail of wind speed distribution. The efficacy of the first-order method is examined. The influences of the type of distributions and the variations of annual maximum wind speed and extreme load coefficient on the predictions are quantified. Finally, the first- and full-order methods are extended to wind load effects of dynamically sensitive structures which facilitate a comprehensive probabilistic analysis as compared to the Monte Carlo simulation schemes used in literature. It is pointed out that 78% fractile extreme load coefficient can be used for defining the characteristic load effects of both rigid and dynamically sensitive structures. The wind load factor is insensitive to the variation of extreme load coefficient. It can be approximately estimated through the wind speed factor and the growth rate of extreme wind load effect with increasing wind speed. The result concerning the wind load factor justifies the advantage of specifying design wind speeds with various MRIs in reducing the uncertainties of design wind loading. DOI: 10.1061/(ASCE)EM.1943-7889.0000118 CE Database subject headings: Wind loads; Uncertainty principles; Reliability; Probability; Aerodynamics. Author keywords: Wind; Wind load; Wind load effect; Uncertainty; Reliability analysis; Probabilistic analysis; Wind load factor; Rigid structures; Dynamically sensitive structures.

The coastal region of China suffers from severe typhoons. Hazard mitigation and risk management require a good estimation of the typhoon wind speed. In this study, an enhanced circular subregion method (CSM) is proposed. The efforts are mainly made in three aspects. First, a new treatment is developed to model the observed central pressure difference better. Second, the appropriate size for the enhanced CSM is discussed. Studies indicate that 500 km is appropriate. Third, Nataf transformation is introduced to incorporate the correlations among typhoon key parameters in wind hazard estimation. The enhanced CSM combined with a typhoon wind field model is used to assess the typhoon hazard for nine cities located in the coastal region of mainland China. Results show the design wind speeds predicted by traditional CSM are lower than those by the enhanced CSM for nine cities with an averaged difference of 4.3% for 50-year and 4.9% for 100-year return periods. The maximum difference was 6.1% in Fuzhou for 100-year return periods. Results also show the consideration of correlations among typhoon key parameters results in a change of the design wind speed at less than 2% for nine cities. Note that the consideration of correlations may not be neglected in other countries. [ABSTRACT FROM AUTHOR]

Architectural facades including balconies, mullions, shading boards, and ribs are widely used outside of tall buildings for the purpose of aesthetics and function. And these facades will affect the wind loads of tall buildings, such as the local wind pressure and aerodynamic force. Thus, to study the influence of architectural facades on wind loads of tall buildings is an important task in wind resistant design. However, most studies focus on the effect of the architectural facade on the local wind pressure using wind tunnel experiments. In the present paper, multiple point synchronous pressure measurements and high-frequency force balance (HFFB) experiments for tall buildings with various architectural facades are conducted to study the influence of different horizontal facades and vertical facades on the local wind pressures and the aerodynamic forces. The results show that the facade may have a significant influence on the local wind pressure and aerodynamic force, and the facade itself may suffer from the larger force. [ABSTRACT FROM AUTHOR]

Traffic signal structures are very susceptible to wind-induced vibration because of their slenderness and low damping. In the wind, the vertical vibration is usually dominant, which affects driving safety and structural fatigue life. To suppress the vibration, a new type of pounding tuned mass damper (PTMD) is proposed in this study. It is specially designed for a cantilevered traffic signal structure with two improvements based on the original PTMD. First, the proposed PTMD has a hidden design and is housed inside the cantilevered mast arm of traffic signal structures, which can avoid visual interference and potential safety risks to drivers and pedestrians. Second, the static equilibrium position of PTMD is relocated so that its mass block just touches the lower boundary of mast arm, which makes it effective at any level of amplitude. Concretely, the mass block pounds the lower boundary of the mast arm under small-amplitude vibrations, while it pounds both the lower and upper boundaries under large-amplitude vibrations. The model experiment on a traffic signal structure was designed to verify the performance of the proposed PTMD in free and forced vibrations. Further, the corresponding numerical simulations were also carried out, where a nonlinear viscoelastic model was established to model the impact force and the related model parameters were obtained by the experimental results. Both numerical and experimental results show that the proposed PTMD is very effective in reducing the vibration of traffic signal structures. [ABSTRACT FROM AUTHOR]

The spectral matrix decomposition is a significant task for a wind velocity field simulation. However, the decomposition requires significant computational time and memory for large-scale structures with a large number of simulation points. To reduce the computational demand, the explicitly expressed Cholesky decomposition of a spectral matrix has been used widely to simulate the wind velocity field evenly distributed along a horizontal axis. In this study, a new closed-form solution of the Cholesky decomposition is proposed for the wind velocity field simulation in which the simulation points can be arbitrarily distributed along the horizontal axis, the autospectra at various points can be different, and the wave passage effect can be considered. Additionally, this closed-form solution is extended to the wind velocity fields along vertical and inclined axes with little approximation. Further, the proposed approach is applied to the nonstationary wind velocity field simulation and random vibration analysis. Finally, numerical examples demonstrate that the proposed approach has good performance. [ABSTRACT FROM AUTHOR]

The simulation and peak value estimation of non-Gaussian wind pressures are important to the structural and cladding design of the building. Due to its straightforwardness and accuracy, the moment-based Hermite polynomial model (HPM) has been widely used. However, its effective region for monotonicity is limited, resulting in its unsuitability for non-Gaussian processes whose skewness and kurtosis are out of the effective region. On the other hand, the Johnson transformation model (JTM) has attracted attention due to its larger effective region compared with that of the HPM. Nevertheless, the systematic study of its application to the simulation and peak value estimation of non-Gaussian wind pressures is less addressed. Specifically, its comparison with the HPM is not well discussed. In this study, a set of closed-form formulas to determine the relationship between correlation coefficients of the non-Gaussian process and those of the underlying Gaussian process was derived, and they facilitate a JTM-based simulation method for the non-Gaussian process. Analytical expressions for the non-Gaussian peak factor were developed. Furthermore, the JTM was systematically compared with the HPM in terms of the translation function, which helps to understand the ensuing performance evaluation on these two models in the simulation and peak value estimation based on the very long wind pressure data. Results showed that the JTM-based peak value estimation method performs well for wind pressures with weak to mild non-Gaussianity, even those beyond the effective region of the HPM, although it may provide slightly worse estimation for strong softening processes compared with the HPM. [ABSTRACT FROM AUTHOR]

The frequency domain approach (FDA) based on the power spectral description of input and output has been widely applied in the random vibration analysis of structures because of its high efficiency and distinct relationship between the input and output. However, for large structures with closely spaced natural frequencies and nonproportional damping, the efficiency of this method for nonstationary response analysis is impacted by the high demand posed by the time-history analysis. In this study, a fast convolution integration method based on Duhamel integration is introduced to enhance the efficiency of the FDA for the nonstationary response analysis of nonproportionally damped structures. First, an efficient impulse excitation approach is proposed to identify the discrete-time impulse response of linear structures. Accordingly, the nonstationary response statistics can be directly evaluated by the convolution with respect to the discrete-time impulse response. Subsequent application of the fast Fourier transform (FFT)–based algorithm accelerates the evaluation of the convolution. Therefore, the proposed scheme is efficient as it eliminates a direct time-history analysis and benefits from the implementation of the FFT. The proposed method is also illustrated to enhance the analysis of nonlinear structures under nonstationary random excitations by invoking an equivalent statistical linearization scheme. Finally, numerical examples are presented to demonstrate the accuracy and efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

Based on the fast Fourier transform (FFT), an efficient and accurate algorithm was developed for improving the computational efficiency of structural responses under nonstationary stochastic excitations. In this method, the FFT technique was first adopted to accelerate the evaluation of time integration terms involving significant computational effort in the nonstationary stochastic response analysis of linear structures. Then, the proper orthogonal decomposition was used to assist the application of FFT for the generally modulated excitation by separating the frequency item of nonuniform modulation functions from the time integration terms. Further, the proposed method was extended to the nonstationary stochastic response analysis of nonlinear structures based on the equivalent statistical linearization method. Finally, numerical examples with respect to linear structures, Duffing systems, and hysteretic systems illustrated that the proposed method performs well. [ABSTRACT FROM AUTHOR]

Estimating the peak value of wind load effects is an important task for engineers of structural and cladding design. Because of the various sources of uncertainties, such as the aerodynamic effect, model selection, and calibration errors, the peak wind load effects may have large variations. This study evaluates the uncertainty of the peak value of wind load effects across multiple samples from a wind tunnel. The Hermite polynomial model (HPM)-based translation process method is adopted to estimate the peak wind load effect. An empirical formula is proposed to estimate the parameters of peak value distribution. Two analytical approaches to model the uncertainty of the peak value at any fractile are proposed based on the probability function and the Gaussianity inference of the peak value. Numerical examples including the wind pressure coefficient and wind-induced response illustrate the performance of the proposed approaches. [ABSTRACT FROM AUTHOR]

The classical spectral representation method for simulation of multivariate nonstationary Gaussian random processes may be less efficient due to difficulty in a straightforward application of the fast Fourier transform (FFT). Although several attempts have been made to invoke the FFT, there remains the need to further improve the efficiency for cases where a large number of points need to be simulated. In this paper, a stochastic wave-based simulation scheme for the multivariate nonstationary random process along a straight line is introduced in conjunction with either a direct summation of cosine functions or the application of a two-dimensional (2D) FFT. Central to the proposed schemes is the transformation of the simulation of a multivariate nonstationary random process to that of a nonstationary one-dimensional stochastic wave. The stochastic wave can be simulated based on a direct summation of cosine functions or by invocation of a 2D FFT. The latter requires that the points to be simulated are evenly distributed. To implement FFT, proper orthogonal decomposition (POD) is employed to factorize the time-dependent and space-dependent 2D decomposed evolutionary power spectral density of the converted stochastic wave. The proposed hybrid approach of a stochastic wave and POD is quite general, and can be used to simulate nonstationary multivariate random processes with complex coherence functions. Numerical examples show that the proposed hybrid approach is very efficient in comparison with existing approaches when the number of simulation locations is large, and it offers a desired level of simulation accuracy when appropriate discretization parameters are selected. [ABSTRACT FROM AUTHOR]

This paper addresses the optimization of an earthquake-resisting system (ERS) and pushover analysis in design of the approach spans of the new South Park Bridge in Seattle, Washington. An appropriate ERS is desired in bridge design, and it involves the application of both pinned column hinges and plastic hinges in seismic analysis to properly allocate the internal forces among bridge substructure components. The approach to derive the ERS is discussed. Conventionally, the column hinge is often modeled as a pinned hinge in pushover analysis, corresponding to the modeling in seismic elastic and plastic hinging analyses. In this design, the column hinge was also modeled as a plastic hinge with limited moment capacity. This novel modeling not only improves the performance-based design but also leads to new insights into pushover analysis. Finally, the design of intermediate piers is presented. [ABSTRACT FROM AUTHOR]